1. Field of the Invention
The present invention relates to method and apparatus for reproducing information added with an error correction code from a recording medium.
2. Related Background Art
In recent years, with the development of the information society, a number of recording media are used. In association with it, a management system to maintain the reliability of the information recording media has also become important. Disk-shaped media and card-shaped media such as magnetic recording medium, optical recording medium, and the like have been known as information recording media. However, in such media, reading errors occur because of physical scratches of the medium itself, dust deposited on the surface of the medium upon reading thereof, or a certain kind of time-dependent change due to an environmental factor. Among the errors, those causes are serious and there is also an error (burst error) such that an error is always generated irrespective of timing and the error cannot be corrected even if the error correction is executed by using an error correction code. However, in the case where the causes of the errors are relatively insignificant, for instance, a reading error which is generated due to a small scratch or dust or a reading error (byte error) which is generated due to a time-dependent change which gradually progresses becomes an error or does not become an error in dependence on the reading timing.
Ordinarily, in the information reproducing apparatus, upon reading, the error correction code is read out together with the information and the error correction is executed. When the degree of error exceeds the error correcting capability, the reading operation is retried. Although it is better if the information can be accurately reproduced by repeating the retry of the error correction a number of times, if the error correction cannot be executed, the information cannot be reproduced.
The case where the information which was initially set at the correctable level becomes unreproducible because errors gradually increase and cause a problem. In this case, if the information is not backed up, it will be permanently lost. Moreover, since the error correction is automatically executed in the reproducing apparatus, the user cannot sense such an increase in errors at all.